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Wet start to September, followed by cool temperatures

September 07, 2018

Wet start to September, followed by cool temperatures:

With measurable rainfall on four of the first five days of the month, suffice to say September started off wetter than normal for many parts of Minnesota. Most of the heavier rains followed the closing of the Minnesota State Fair, which set record attendance this year of well over 2 million people over the 12-day run.

For the first week of the month Winona (Winona County), Theilman (Wabasha County), and Owatonna (Steele County) all report 5 or more inches of rain so far. Most of the heavier doses of rain (1-3 inches) fell over portions of southern and central Minnesota and came on the 4th and 5th, fueled in part by dew points in the 70s F. Some of the rainfall set new daily records in places such as Rochester with 3.32 inches and Granite Falls with 2.43 inches on the 4th. Other places reported new daily record amounts for the 5th. Too numerous to list all of them, some of those with longer climate histories that set new daily rainfall records on September 5th were:

Caledonia (Houston County) is now up to nearly 46 inches of precipitation for the year so far, while many other southern Minnesota climate stations are on a pace to perhaps set a record as the wettest year.

Following the passage of the cold front on the 5th temperatures cooled down significantly. By Thursday and Friday mornings, September 6-7 portions of St Louis, Lake, Cook, Koochiching, Lake of the Woods, and Itasca Counties reported frosts, and some morning lows in the upper 20s F (28°F at International Falls). Many daytime highs remained in the 60s F as well.

Weekly Weather Potpourri:

The NOAA National Hurricane Center has had a busy week tracking a number of tropical weather events. Remnants of Tropical Storm Gordon were bringing rain to southern Illinois and Kentucky, while Tropical Storm Florence, expected to grow into a hurricane, was being watched in the mid-Atlantic Ocean, and Hurricane Olivia was being monitored in the Eastern Pacific Ocean as it heads towards Hawaii, perhaps by the middle of next week.

The United KingdomMeteorological Office issued a statement this week that the summer of 2018 (June-August) across England, Scotland and Wales was so warm it tied 1976, 2003, and 2006 for the hottest ever summer historically.

A new study in the journal Science suggests large-scale wind and solar farms if deployed in the Sahara region of Africa could increase rainfall and promote more widespread vegetation.

MPR listener question:

We live in south Minneapolis not far from the airport and have kept a backyard rain gage record for the past 28 years. It seems like we have had less than the usual number of rainy days so far this year (days with measurable rainfall). Is this true?

Answer:

For the period January through August of 2018 the MSP airport has reported measurable precipitation so far on 73 days. Perhaps that is close to your number since you live so close. The long term historical average for this period is 80 days, so you are correct in perceiving fewer days with measurable precipitation. Incidentally in 1991, a very wet year, there were already 100 such days.

Twin Cities Almanac for September 7th

The average MSP high temperature for this date is 75 degrees F (plus or minus 9 degrees F standard deviation), while the average low is 56 degrees F (plus or minus 7 degrees F standard deviation).

Average dew point for September 7th is 54 degrees F, with a maximum of 75 degrees F
in 1985 and a minimum of 34 degrees F in 1956.

All-time state records for September 7th:

The all-time state high temperature for today's date is 104 degrees F at Wadena (Wadena County) in 1931; the all-time state low for today's date is 20 degrees F at Tower (St Louis County) in 1986. The all-time state record precipitation for this date is 8.70 inches at Tower (St Louis County) in 2007. There has been no record of snowfall on this date.

Past Weather Features:

By far the warmest September 7th in state history was in 1931 when over 40 climate stations reported afternoon high temperatures of 90 degrees F or greater. Seven communities reached 100 degrees F or greater and even overnight temperatures remained in the 70s F across western Minnesota.

Widespread frosts greeted campers in northern Minnesota on the morning of September 7, 1986 as low temperatures ranged from 26 to 32 degrees F in many places.

A band of heavy thunderstorms crossed northeastern Minnesota over September 6-7, 2007 bringing record setting rainfall. Portions of St Louis and Lake Counties reported 6-8 inches of rain, flooding many roads and highways there.

Outlook:

Sunny and pleasant throughout the weekend, with a warming trend starting next week that will produce above normal temperatures by mid-week. There is little chance for rainfall until the middle of next week.

Comments

A question. The MN DNR Hunting Regulations booklet shows approximately 30 minutes difference in sunset times from extreme eastern MN to extreme western MN. It seems like there should also be a difference from north to south. Is there a significant difference?